Pulsed laser deposition (PLD) in which pulses of laser radiation are used to evaporate material from a target which is then deposited on a substrate represents a breakthrough in methods for the production of technologically important thin films. Versatility and simplicity are essential features of pulsed laser deposition as a technique for depositing thin films of complex materials. Virtually any material, from pure elements to multicomponent and organic compounds can be deposited; and the stoichiometry of the target material is faithfully reproduced in the film.
Advantages of PLD stem from the fact that laser beams, unlike ion beams or electron beams, are easy to transport and manipulate, and the dynamic range of delivered energy is the largest compared to virtually any deposition process. As a result, PLD has the highest instantaneous deposition rate, up to 100 times higher than in other thin film deposition methods such as Chemical Vapour Deposition. Molecular Beam Epitaxy. Plasma Processing, Magnetron and RF Sputtering, and others. Nevertheless, pulsed laser deposition has not become widely used as a thin film production method for important technologies such as the semiconductor electronics industry or photonics, because of the creation of particulates during PLD which prevent the formation of suitably high quality films.
This major disadvantage is well known using conventional PLD methods, where it is normal to employ low repetition rate, powerful nanosecond-range laser pulses to evaporate the target. In this situation large numbers of macroscopic particles and droplets, having a typical size from a fraction of a micron to a few microns, are ejected from the target during the evaporation process. As a consequence, the convention PLD process cannot provide good surface quality or uniformity of the deposited films since these particles and droplets become embedded in the resulting film. The particulate problem severely limits the commercial applications of the existing pulsed laser deposition technique. In high-performance electronic and in optical applications such as optical thin film devices with sophisticated architecture, stringent constrains exist for surface smoothness; therefore the tolerance of particulate density and size is generally very low, in order&lt;1 particle per mm.sup.2.